Revision control
++ // Copyright (C) 2024 Intel Corporation.
++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
++ // Qt-Security score:significant reason:default
++
++ #ifndef QLATCH_P_H
++ #define QLATCH_P_H
++
++ //
++ // W A R N I N G
++ // -------------
++ //
++ // This file is not part of the Qt API. It exists purely as an implementation
++ // detail. This header file may change from version to version without notice,
++ // or even be removed.
++ //
++ // We mean it.
++ //
++
++ #include <QtCore/qbasicatomic.h>
++ #include <QtCore/qtsan_impl.h>
++
++ #include <private/qglobal_p.h>
++
++ #include <limits>
++
++ QT_BEGIN_NAMESPACE
++
++ class QLatch
++ {
++ public:
++ constexpr explicit QLatch(int expected) noexcept
++ : counter(expected | NoWaiters)
++ {}
++
++ int pending() const noexcept
++ {
++ return (counter.loadAcquire() & CounterMask);
++ }
++
++ void countDown(int n = 1) noexcept
++ {
++ QtTsan::latchCountDown(&counter);
++ if (counter.fetchAndSubRelease(n) == n) // addAndFetch(n) == 0
++ wakeUp();
++ }
++
++ bool tryWait() const noexcept
++ {
++ if (pending() != 0)
++ return false;
++ QtTsan::latchWait(&counter);
++ return true;
++ }
++
++ void wait() noexcept // not const
++ {
++ if (int current = counter.loadAcquire(); (current & CounterMask) != 0) {
++ waitInternal(current);
++ QtTsan::latchWait(&counter);
++ }
++ }
++
++ void arriveAndWait(int n = 1) noexcept
++ {
++ countDown(n);
++ wait();
++ }
++
++ // API compatible with C++20:
++ static constexpr int max() noexcept { return std::numeric_limits<int>::max(); }
++ void count_down(int n = 1) noexcept { countDown(n); }
++ bool try_wait() const noexcept { return tryWait(); }
++ void arrive_and_wait(int n = 1) noexcept { arriveAndWait(n); }
++
++ private:
++ static constexpr int NoWaitersBit = 31;
++ static constexpr int NoWaiters = 1 << NoWaitersBit;
++ static constexpr int CounterMask = ~NoWaiters;
++ QBasicAtomicInt counter;
++
++ Q_DISABLE_COPY_MOVE(QLatch)
++
++ #ifdef QATOMICWAIT_USE_FALLBACK
++ # define Q_LATCH_EXPORT /* being linked into the unit test */
++ #else
++ # define Q_LATCH_EXPORT Q_CORE_EXPORT
++ #endif
++
++ void Q_LATCH_EXPORT waitInternal(int current) noexcept;
++ void Q_LATCH_EXPORT wakeUp() noexcept;
++
++ #undef Q_LATCH_EXPORT
++ };
++
++ QT_END_NAMESPACE
++
++ #endif // QLATCH_P_H